diff --git a/src/coverage/CoverageSimplifier.cpp b/src/coverage/CoverageSimplifier.cpp
index 73b5a5e442..335b107597 100644
--- a/src/coverage/CoverageSimplifier.cpp
+++ b/src/coverage/CoverageSimplifier.cpp
@@ -20,6 +20,7 @@
 #include <geos/geom/Geometry.h>
 #include <geos/geom/GeometryFactory.h>
 #include <geos/geom/MultiLineString.h>
+#include <geos/util/IllegalArgumentException.h>
 
 
 using geos::geom::Geometry;
@@ -83,7 +84,12 @@ CoverageSimplifier::simplifyInner(
 CoverageSimplifier::CoverageSimplifier(std::vector<const Geometry*>& coverage)
     : m_input(coverage)
     , m_geomFactory(coverage.empty() ? nullptr : coverage[0]->getFactory())
-    {}
+    {
+        for (const Geometry* g: m_input) {
+            if (!g->isPolygonal())
+                throw util::IllegalArgumentException("Argument is not a non-polygonal");
+        }
+    }
 
 /* public */
 std::vector<std::unique_ptr<Geometry>>
diff --git a/tests/unit/coverage/CoverageSimplifierTest.cpp b/tests/unit/coverage/CoverageSimplifierTest.cpp
index 61e79f54ec..94534544af 100644
--- a/tests/unit/coverage/CoverageSimplifierTest.cpp
+++ b/tests/unit/coverage/CoverageSimplifierTest.cpp
@@ -431,7 +431,7 @@ void object::test<24> ()
             "POLYGON EMPTY",
             "POLYGON EMPTY" })
     );
-  }
+}
 
 // testOneEmpty
 template<>
@@ -446,7 +446,7 @@ void object::test<25> ()
             "POLYGON ((1 9, 9 9, 9 1, 1 1, 1 9))",
             "POLYGON EMPTY" })
     );
-  }
+}
 
 // testEmptyHole()
 template<>
@@ -461,6 +461,26 @@ void object::test<26> ()
             "POLYGON ((1 9, 9 9, 9 1, 1 1, 1 9), EMPTY)",
             "POLYGON EMPTY" })
     );
-  }
+}
+
+// Test non-polygon inputs (GH-1031)
+template<>
+template<>
+void object::test<30> ()
+{
+    auto input = readArray({
+        "MULTILINESTRING ((200 100, 100 100, 200 200), (200 200, 200 100), (200 200, 300 100, 200 100))"
+        });
+    try {
+        std::vector<std::unique_ptr<Geometry>> result =
+        CoverageSimplifier::simplify(input, 10);
+    }
+    catch (geos::util::IllegalArgumentException& iae) {
+        ensure("caught IllegalArgumentException", true);
+        return;
+    }
+    ensure("did not throw IllegalArgumentException", false);
+}
+
 
 } // namespace tut